Method of obtaining naphthenic acids



Patented Oct. '29, 1940 UNITED S ATES METHOD OF OBTAINING NAPHTHE'NIC ACIDS Johannes H. Bnmn', Swarthmore, Pa., assignor to Sun Oil Company, Philadelphia, Pa., a corporationof New Jersey No Drawing. Application April 16, 1935, Serial No. 16,607

13 Claims.

where an. addition of sodium hydroxide or otheralkali is made before or during the distillation, sodium, or other alkali metal soaps of petroleum naphthenic or fatty acids are formed. Similarly to most inorganic sodium salts, these soaps cannot be distilled by ordinary methods and consequently may remain in the still bottoms. This is true regardless of what type of crude the stock being distilled may be derived from, but in the case of paraflln or some predominately paraflln mixed base crudes the percentage of soaps will be materially less. The largest amount of soaps will be formed in the distillation of true asphaltic crudes, a lesser percentage in mixed base, and a still smaller percentage in paramn base crudes. In fact, the recovery of soaps from paramnic crude residues may not be important from the standpoint of soap recovery but important only as a means of freeing the bottoms of soaps to render them non-emulsiflable.

If the crude is a "coastal type asphaltic base,

n, may vary from,16 to 40. Thus there would be present the soaps of the several acids of each series, the soaps probably beingas follows;

'CmHrICOONa CrIHrQCOONa 'fCraHznCOONa' lQaoHsaCQONB. U CzrHasCOONa CzsHaoCOONa. CMHaoCOONa C25H41COONa CavHcsCOONa as (3) and possibly others 1,761,153,i'ss'ued June 3,1930, the'bottoms re-.

For these formulas, the number of carbon atoms,

which have not yet been isolated. The total amount of such acids present in this type of crude, before distillation, may be about .7%.

A mixed base crude would probably contain' some of the acids mentioned above and in ad- 5 dition would probably contain some acids of the series whose general formula is Cal-12,1402. The total acid content of this type crude would be somewhat less than that of a coastal type" asphaltic base crude.

- A paramn base crude, such as a Pennsylvania crude, would have a very low acid content, probably about .03% and would consist predominately of acids of the series whose general formulae is CnH2nO2 and chm-=0:- 1

The still bottoms, containing the sodium or other alkali metal soaps of the above mentioned petroleum naphthenic acids, may be treated in accordance with the present invention to remove these soaps, in case a paraflln base crude is being 20 distilled, or to recover the valuable petroleum naphthenic acids corresponding thereto, in case 3m mixed base or asphaltic base crude is being dis- I have discovered that these petroleum .naph- 2 thenic acids are soluble in liquefied normally gas- 1 eous hydrocarbons, or mixturesof the same; such. as propane or commercial mixtures of propane with other normally gaseous hydrocarbons, such as propylene, butane, iso-butane, and the like, while the sodium or other alkali metal soapsof these acids are insoluble in such liquefied normally gaseous hydrocarbons. Certain other constituents of the still bottoms are soluble in propane at normal or slightly elevated temperatures, principallyany heavy lubricating oil which was notv distilled over during the distillation. Such oil is a very heavy and viscous one, having a high flash point and is quite valuable. It hasv heretofore been impossible to recover such heavy oil free from the alkali soaps of the petroleum naphthenic acids contained in thestill bottoms;

When a coastal type asphaltic base crude is being distilled the still bottoms will consist ofv about 12 parts of naphthenic acids of the type enumerated above and about 18 parts of asphalt havin a meltin mini. m' ahnui'. son-315 FL and containing petroleum resins and other asphaltic impurities.

Since the still bottoms are very viscous and tarry they may be mixed with approximately one-third their weight of water in order to facilitate handling, thereby forming an emulsion. While the addition of water to the still bottoms to form an emulsion is not absolutely necessary, it is preferred since it not only facilitates the handling of the still bottoms, but also materially decreases the time necessary for separation into definite layers of the mass being extracted. So

long as the petroleum naphthenic or fatty acids are present in the form of sodium soaps, these soaps with the water and asphaltic impurities will form a' homogeneous mass of higher specific gravity than the soaps and aspha-ltic impurities alone, and will separate more readily from the propane layer which contains the dissolved minabout 125-130 F. The lubricating oil contained in the still bottoms is readily dissolved in the propane under these conditions, and, if the mixture is allowed to stand, the propane with the lubricating oil dissolved therein will readily separate from the mixture of soaps,. asphalt and water. The mixture of soaps, asphalt and water may then be drawn ofi, separately from the solution of oil and propane. The solution of oil and propane may then be distilled to separate the propane from the oil. After the oil has been removed from the still bottoms, the separation of the soaps of the petroleum naphthenic acids from the asphalt may be accomplished quite readily by merely heating the mixture of soaps, asphalt and water for 10-15 minutes, and then drawing of! the asphalt. Or it is apparent that these soaps may be separated from the asphalt by the pressure settling method described in Angstadt Patent No. 1,931,880. Or by acidification, by usual methods, of the soap of the said.mixture, the naphthenic acids will separate out and may be recovered. These acids may then be dehydrated or, if desired, they may be further purifled, as by propane extraction, as hereinafter more fully described, to remove the last traces of asphaltic impurities.

If the acidification method Just specified be adopted, then, instead of separating out the naphthenic acids, the mixture may be mixed with 4 or 5 volumes-of liquefied propane, which will dissolve the acids. The propane with the acids dissolved therein may then be separated from the asphalt, and the propane distilled off to leave the purified acids.

The purified acids obtained as above outlined will have a saponiflcation value of 80-160 mg. KOH per grain and are most suitable, when again saponified, for use in preparing soluble oils and oil emulsions of all kinds.

This same method is equally advantageous for use in purifying petroleum naphthenic acids which have been obtained from the still bottoms by some other method, for instance, by the pressure settling method described in Angstadt Patent No. 1,931,880. The crude sodium soaps of these naphthenic acids obtained by the method outlined in the above patent, contain appreciable quantities of impurities, consisting in the main of the heavy lubricating 011 above described and asphalt, petroleum resins and other asphaltic impurities. The asphaltlc impurities impart a dark color to the acids and it is necessary to remove them in order to render them fit for sale.

' The. presence of the lubricating oil in the acids dilutes them and thus decreases their saponiflcation value. However, in many of the uses to which these acids are put, they are again saponified and mixed with a mineral oil to form an emulsifying oil, so it may not be necessary to remove the heavy oil from the acids. When it is desired to remove the oil from the crude acids obtained by the pressure settling method, these crude acids in the form of their sodium soaps are first mixed with three or four volumes of liquefied propane, preferably with heating to 125- 130 F., and with stirring or other agitation. As hereinbefore stated, the lubricating oil is readily dissolved by the propane under these conditions, while the sodium or other alkali soaps of the naphthenic acids and the asphaltic impurities are not dissolved. The propane with the mineral oil dissolved therein is separated from the soaps of the naphthenic acids and asphaltic impurities, and the mineral oil may then be recovered by distilling oh? the propane. The residuum from the propane extraction which consists of the soaps of the naphthenic acids and asphaltic impurities may then be acidified by known methods to break down the soaps to form the corresponding naphthenic acids.

To this mixture of naphthenic acids and asphaltic impurities is added four to five volumes of liquefied propane, and this mixture is thoroughly mixed preferably while heated to about of asphaltic impurities and the acids are recovered by distilling off the propane.

This same procedure may be used to separate the naphthenic acids or their sodium soaps from the still bottoms remaining after any type of crude has been distilled. Thus, if a paraffinic' base crude is being distilled, the still bottoms will consist predominately of heavy lubricating oil, which could not be distilled without cracking, paraffin wax, and a very small percentage of the sodium soaps of petroleum naphthenic acids. By adding 4 or 5 volumes oil-liquefied propane to these still bottoms and thoroughly mixing them while heating them to 125-130 F., the heavy lubricating oil and wax will be dissolved while the alkali metal. soaps of the petroleum naphthenic acids will not be dissolved. The mixture of liquefied propane, oil, and wax may then be separated from the alkali metal soaps of the petroleum naphthenic acids, and the propane may be removed from the oil by distillation or it may be left in the oil to serve as a diluent during dewaxing.

It is to be understood that throughout the various propane extraction steps, sufiicient pressure will be maintained on the propane .to keep it in liquid form. Thus, when the propane is heated to 125-130 F., a pressure in excess of 282 pounds tained therein. It is also to be understood that temperatures higher than 125-130 F. may be used, but are not desirable due to the high pressures. Likewise, lower temperatures may be used but in such a case a longer period of time must be allowed for the propane to thoroughly dissolve the various constituents being extracted, or the ratio of propane to the material undergoing extraction must be increased.v

By the method described above, I am able to obtain from the still bottoms remaining after the distillation in the presence of an alkali, of a mineral oil, a valuable heavy lubricating oil, which heretofore could not be recovered, or else was recovered only after severe treating which caused high losses. I also obtain pure petroleum naphthenic acids having a saponification value of 80-160 mg. KOH per gram, which in themselves are very valuable. Also, if the oil distilled is one which contains asphalt, I recover an excellent grade of non-emulsifiable asphalt, which may be blended with other asphaltic oils or residues to produce an asphalt to meet any requirements. r h

Where the term liquefied normally gaseous hydrocarbons is used in the following claims, it is to be understood that I intend this term to include such liquefied normally gaseous hydrocarbons as propane, propylene, butane, isobutane, and the like or mixtures of the same.

I do not herein claim that part of the herein described process which comprises the separation of the alkali soaps of petroleum naphthenic and fatty acids from a mixture of the same with asphalt by acidifying the mixture to convert the alkali soaps into their corresponding naphthenic acids, mixing the thus acidified mixture with liquefied propane to dissolve the petroleum naphthenic and fatty acids, and separating the liquefied propane with the petroleum naphthenic and fatty acids dissolved therein from the asphalt, since'this method is the subject matter of my copending application, Serial No. 62,436, filed February 5, 1936;

What I claim and desire to protect by Letters Patent is as follows:

1. The method of separating the alkali metal soaps of petroleum naphthenic and fatty acids and other impurities from the heavy lubricating oil remaining in the still bottoms after a crude petroleum has been distilled in the presence of an alkali, which comprises mixing said still hottoms with a liquefied normally gaseous hydrocarbon to dissolve said heavy lubricating oil, andseparating said liquefied normally gaseous hydrocarbon with said mineral oil dissolved therein from said soaps.

2. The method of separating the alkali metal soaps of petroleum naphthenic and fatty acids and other impurities from the heavy lubricating oil remaining in the still bottoms after a crude petroleum has been distilled in the presence of an alkali, which comprises mixing said still botin said still bottoms; separating said liquefied normally gaseous hydrocarbon with the lubricating oil dissolved therein from the asphaltic re-.

after distilling a crude petroleum in the presence of an alkali and which contain such petroleum naphthenic acids in the form of their alkali metal soaps in admixture with heavy lubricating oils, asphalt, petroleum resins, and other asphaltic impurities, which comprises mixing said still bottoms with a small amount of water to form an. emulsion, mixing said emulsion with a liquefied normally gaseous hydrocarbon to dissolve the heavy lubricating oil, separating said liquefied normally gaseous hydrocarbon with said heavy lubricating oil dissolved therein from a residue of said soaps, said asphaltic impurities and said water, acidifying said residue to break down said soaps to form the corresponding petroleum naphthenic acids, and separating said petroleum naphthenic acids from said water, asphalt, petroleum resins, and other asphaltic impurities.

5. The method of recovering petroleum naphthenic and fatty acids'from the still bottoms remaining after distilling a crude petroleum in the presence of an alkali and which contain such petroleum naphthenic and fatty acids in the form of their alkali metal soaps in admixture with heavy lubricating oil, asphalt,petroleum resins, and other asphaltic impurities, which comprises mixing said still bottom with a liquefied normally gaseous hydrocarbons to dissolve said heavy lubricating oil, separating said liquefied normal- 1y gaseous hydrocarbon with said heavy lubricating oil dissolved therein from a residue of said soaps, asphalt, petroleum resins and other asphaltic impurities, acidifying said residue to break down said soaps to form their corresponding acids, mixing said acidified residue with a liquefied normally gaseous hydrocarbon to dissolve said petroleum naphthenic and fatty acids, separating said liquefied normally gaseous hydrocarbon with said petroleum naphthenic and fatty acids dissolved therein from said asphalt, petroleum resins and other asphaltic impurities, and removing said liquefied normally gaseous hydrocarbon from said naphthenic and fatty acids.

6. The method of recovering petroleum naphthenic and fatty acids from a crude starting material containing such acids in the form of their alkali metal soaps in admixture with heavy lu bricating oil, asphalt, petroleum resins and other asphaltic impurities which comprises; mixing said crude material with a liquefied normally gaseous hydrocarbon to dissolve said heavy lubricating oil; separating said liquefied normally gaseous hydrocarbon with said heavy lubricating oil dissolved therein from a residue of said soaps, asphalt, petroleum resins and other asphaltic impurities; acidifying said residue to break down said soaps to form their correspondingacids; mixing said acidified residue with a liquefied normally gaseous hydrocarbon to dissolve said petroleum naphthenic and fatty acids; separating said liquefied normally gaseous hydrocarbon with said petroleum naphthenic and fatty acids dissolved therein from said asphalt, petroleum resins and other asphaltic impurities and removing said liquefied normally gaseous and fatty acids.

oil remaining in still bottoms resulting from distilling crude petroleum. in the presence of an alkali, which comprises mixing said still bottoms with liquefied propane to dissolve said heavy lubricating oil, and separating. the liquefied propane with said mineral oil dissolved therein from said metal soaps.

9. Ina process of separating lubricating oil from a mixture of soaps of naphthenic acids and lubricating oil, the steps of diluting said mixture with a liquefied normally gaseous hydrocarbon and separating the oil-soluble phase from the naphthenic acid' soaps.

10. In a process of separating lubricating oil from a mixture of soaps of naphthenic acidsand lubricating oil, the steps of adding water to the mixture, diluting the mixture with a liquefied normally gaseous hydrocarbon and separating the oil-soluble phase from the aqueous phase hydrocarbon from said petroleum naphthenicv 11. In a process of purifying crude naphthenic acids the steps of diluting the soaps of said acids with a liquefied normally gaseous hydrocarbon and separating the oil soluble phase from the purified naphthenic acid soaps.

12. A method of treating asphaltic oil containing alkali metal naphthenic acid soaps which comprises mixingsaid oil with a liquefied normally gaseous hydrocarbon solvent to dissolve the ofl, removing the oil dissolved in said solvent from the insoluble residue, acidifying the insoluble residue to liberate the naphthenic acids and removing the free naphthenic acids from the asphalt.

13. A method of treating asphaltic oil containing alkali metal naphthenic acid soaps which comprises mixing said oil witha liquefied normally gaseous hydrocarbon solvent to dissolve the oil, removing the oil dissolved in said solvent from the insoluble residue, acidifying the insoluble asphaltic residue with a mineral acid to liberate the naphthenic acids from the soaps, mixing the acidified residue with a liquefied normal- 1y gaseous hydrocarbon solvent to dissolve the liberated naphthenic acids, separating the solvent solution of naphthenic acids from the undissolved asphalt and removing the liquefied normally gaseous hydrocarbon from the liberate naphthenic acids.

. JOHANNES H. BRUUN. 

